<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="../bootstrap-5.1.3-dist/css/bootstrap.css">
    <script src="../bootstrap-5.1.3-dist/js/bootstrap.js"></script>
</head>

<body class="container">
    <h2 align="center">设置表单控件的大小</h2>
    <form>
        <input class="form-control form-control-lg" type="text" placeholder="大尺寸（form-control-lg）"><br />
        <input class="form-control" type="text" placeholder="默认大小"><br />
        <input class="form-control form-control-sm" type="text" placeholder="小尺寸（form-control-sm）">
    </form>
</body>

</html>